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Author SHA1 Message Date
1f69aa3114 minor corrects to report, add pwm_on_off.svg 2023-11-15 12:24:19 +00:00
39ccb44a50 update readme 2023-11-10 19:13:02 +00:00
3 changed files with 257 additions and 6 deletions

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@@ -7,3 +7,11 @@
Marks: 100% Marks: 100%
[Feedback sheet](./res/prep-feedback.pdf) [Feedback sheet](./res/prep-feedback.pdf)
## Post Lab Coursework
View [lab coursework report](./report.md).
Questions stated in [lab procedure sheet](./res/Lab 1 - Sensors and Encoder - Procedure Sheet and Coursework.pdf).
Marks and feedback pending.

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@@ -26,6 +26,7 @@ uuid: 864e5249-a02c-4896-b274-a0a76789955c
## Question 2 ## Question 2
- 100 % duty cycle PWM is different from all the others as it is not a wave, but just a DC voltage - 100 % duty cycle PWM is different from all the others as it is not a wave, but just a DC voltage
(the entire region is the ON region, hence it is not underlined in the figures)
- Voltage is not zero in the OFF region because the rotational inertia is still spinning the motor, - Voltage is not zero in the OFF region because the rotational inertia is still spinning the motor,
which creates a back EMF, and that is the voltage being read in the OFF region. which creates a back EMF, and that is the voltage being read in the OFF region.
Back EMF is proportional to the speed of the motor, which is why the voltage in the off region is Back EMF is proportional to the speed of the motor, which is why the voltage in the off region is
@@ -37,13 +38,15 @@ uuid: 864e5249-a02c-4896-b274-a0a76789955c
## Question 3 ## Question 3
- The difference between the ON+ and ON- is that the current will go in opposite directions, ![H-Bridge at different states](./images/h-bridge.png)
resulting in the motor spinning in opposite directions
- The default PWM frequency of pin 13 on the Arduino Mega 2560 is 976.5625 Hz [^1]
- The audible frequency we hear is a ~1000 Hz square wave, which can be seen by the fact the period of
the wave in figure below is roughly 1 millisecond
![PWM waveform at 977 Hz](./images/pwm_frequency.jpg) - The difference between the ON+ and ON- in the figure above is that the current will go in opposite
directions, resulting in the motor spinning in opposite directions
- The default PWM frequency of pin 13 on the Arduino Mega 2560 is 976.5625 Hz [^1]
- The audible frequency we hear is a ~1000 Hz square wave, which can be seen by the fact the period
of the wave in figure below is roughly 1 millisecond (see figure below)
![PWM waveform at 977 Hz](./images/pwm_frequency.jpg){ height=2in }
\newpage \newpage